DE 10 2007 010 155 A1 presents a valve drive having a sliding cam element arranged on a carrier shaft, and the sliding cam element can be displaced axially in the axis of rotation of the carrier shaft. On the sliding cam element there is mounted a cam profile group which has different cam profile sections. Depending on the axial position of the sliding cam element, a pick-off element, illustrated as a roller-type rocker lever, can interact with differently contoured cam profile sections of the cam profile group, such that the valve is actuated in a manner dependent on the selected cam profile section. For example, the cam profile sections can be differently contoured such that the valve can perform opening strokes of different magnitude or different length. The roller-type rocker lever has a roller, and on the side averted from the valve, the roller-type rocker lever is supported by way of a valve play compensation element.
The contact between the roller of the roller-type rocker lever and the cam profile section necessitates a minimum width owing to the actuation forces of the valve, and linear contact is formed between the roller and the cam profile section, which linear contact must thus have a minimum length. If the roller is selected to be too narrow, the Hertzian stresses on the surface of the cam profile section become too high, and premature fatigue or surface wear of the valve drive can occur. It is thus disadvantageously necessary for the sliding cam element to be formed with a minimum width which is determined at least by the required width of the cam profile sections, such that a minimum displacement length of the sliding cam element also becomes necessary in order to change over the cam profile section in contact with the roller. However, a sliding element of wide form lengthens the switching times for switching between different cam profile sections in operative connection with the pick-off element, wherein it is basically sought to provide a valve drive in which the fastest possible changeover of the cam profile sections in contact with the pick-off element is possible. In particular in the case of high rotational speeds of an internal combustion engine, the sliding cam element must be moved axially between two positions in very short times, such that a design of a sliding cam element of narrow construction would be expedient.
DE 10 2007 020 128 A1 presents a pick-off element having two rollers which are in contact with a single cam element. Here, the two rollers, which are arranged spaced apart from one another, effect guidance of a receiving rocker which lies in a cam follower and which permits tilting compensation of the cam follower relative to the cam element.